Prior optical protection switching systems are known that employed electromechanical optical switching elements as distributors and selectors.
An electrical 1.times.N distributor switch is an 1.times.N switching device which routes the signal or signals from a single input port to any one of the N output ports. An optical 1.times.N distributor switch is the optical analog of an electrical 1.times.N distributor switch where the input and output ports are optical fibers carrying one or more optical communication signals at a given wavelength or a plurality of wavelengths. Certain distributor switches may permit routing the signal from the input line to two or more of the N output ports, thus dividing the signal energy from the input line among the target output ports. This properly is called the broadcasting or bridging capability of the distributor switch.
An optical N.times.1 selector switch is the optical analog of an electrical N.times.1 selector switch where the input and output ports are optical fibers carrying one or more optical communication signals at different wavelengths. Certain selector switches may permit selection of more than one input port and adding (under certain rules) the signals from the selected ports. This properly is called the collection capability of the selector switch.
A number of electromechanical optical distributor and selector switches are presently available. These devices are based on mechanically moving the input and/or output fibers or utilizing various reflective or deflective optical elements to spatially direct a beam of light from the exit pupil of the input fiber and routing it to the entrance pupils of the output fibers. Clearly, these mechanical switches are slow and, in most cases, do not permit broadcast capability, a desirable feature in communication systems. In some cases, the optical loss associated with these elements is significant.
Such prior cross-connect arrangements employing electromechanical optical distributors and selectors were limited in selecting only one line at a time, their speed was slow, and their reliability was less than desirable.